Method of sintering iron, copper tin alloys followed by slow cooling

ABSTRACT

A sintered shaped body comprises 0.5 to 3% tin, 2 to 14% copper, balance iron, the ratio of tin to copper being between 1:2 and 1: 9. The bodies are made by sintering an alloy as indicated at a temperature of about 900 to 1100*C for a time from about 20 to 60 minutes. The bodies are distinguished by a high elongation at break together with high tensile strength.

finite Sttes tent [191 Esper et a1.

METHOD OF SINTERING IRON, COPPER TIN ALLOYS FOLLOWED BY SLOW COOLING Inventors: Friedrich J. Esper, Leonberg;

Robert Zeller, Stuttgart, both of Germany Robert Bosch GmbI-I, Stuttgart, Germany Filed: June 26, 1972 App]. No.: 266,443

Assignee:

Foreign Application Priority Data Aug. 26, 1971 Germany 2142708 References Cited UNITED STATES PATENTS 7/1967 Oakley 75/200 ec. 10, I974 3,647,573 3/1972 Fuchs et a1. ..75/200 OTHER PUBLICATIONS Esper et al., Sintering Reactions Radial Compression Strength of IronTin and Iron-Copper-Tin Powder Compacts, International Journal of Powder Metallurgy, Vol. 5, N0. 3, 1969, TN695 I56.

Primary Examiner-Benjamin R. Padgett Assistant Examiner-B. Hunt Attorney, Agent, or FirmMichael S. Striker 5 7] ABSTRACT A sintered shaped body comprises 0.5 to 3% tin, 2 to 14% copper, balance iron, the ratio of tin to copper being between 1:2 and 1:9.

The bodies are made by sintering an alloy as indicated at'a temperature of about 900 to l100C for a time from about 20 to 60 minutes.

The bodies are distinguished by a high elongation at break together with high tensile strength.

3 Claims, -1 Drawing Figure METHOD OF SINTERING IRON, COPPER TIN ALLOYS FOLLOWED BY SLOW COOLING BACKGROUND OF THE INVENTION The invention relates to sintered shaped bodies and a process of making the same wherein the alloy involved is tin, copper and predominantly iron.

Sintered alloys of tin, copper, balance iron have long been known. it is also known that by careful selection of the composition fairly good values for the tensile strength can be obtained. However, so far the values for the elongation have always been low. This entire group of alloys, at least to the extent that th e iron portion predominated, was therefore only of very limited use. On the other hand this type of sintered alloy could be of substantial practical interest if one substitutes tin for nickel. The latter requires a substantially lower sintering temperature. Besides nickel is frequently available only with difficulties.

It is therefore an object of the present invention to provide for a tin-copper alloy for shaped bodies which are made by a sintering process in which iron forms the predominant component of the alloy and which nevertheless is distinguished by a high elongation that goes together with high tensile strength.

SUMMARY OF THE INVENTION This object is met by forming the sintered shaped body of an alloy comprising 0.5 to 3% tin, 2 to [4% copper, balance iron, and providing for a ratio of tin to copper within the range of 1:2 and 1:9.

The sintered bodies are made by sintering a powder mixture of the above mentioned composition at a temperature of about 900 to 1 100C for a time from about 20 to 60 minutes.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of the drawing is a graphic representation wherein on the horizontal axis the temperatures are recorded at which the quenching after sintering or the tempering after sintering is performed. The vertical axis shows the values for the elongation at break (8) and the values for the tensile strength The solid curve relates to the elongation at break while the dashed curve represents the tensile strength.

DETAILS OF THE INVENTION AND SPECIFIC EMBODIMENTS A preferred ratio between tin and copper is in the range of 1:4.

All statements made herein regarding the percentages of the components are by weight percentages.

According to a specific embodiment of the invention it is preferred to employ a heat treatment following the sintering step. The sintering itself is preferably carried out at a temperature between 900 and l100 for between 20 and 60 minutes in all three alternative embodiments of the thermal after-treatment. This aftertreatment is effected immediately following the sintering step. The three alternatives are as follows:

A. The shaped bodies immediately after sintering are cooled down to a temperature between 520 and 750C with a rate 2 l5C/min. This is followed by quenching. The specific quenching temperature within the range to which the bodies are cooled depends on the desired values for the elongation at break or tensile strength and can be easily selected according to the accompanying drawing.

B. The formed bodies immediately after sintering are subjected to a slow cooling to room temperature. They are thereafter subjected to a tempering treatment for between 15 minutes and 5 hours at a temperature between 520C and 750C. This is followed by quenching. The specific'tempering temperature within the range stated again depends on the desired values for the elongation at break or the tensile strength which can be found in the attached drawing.

C. The formed bodies are cooled to a temperature of 300C with a cooling speed 27C/min. After that they are permitted to cool in a protective gas atmosphere.

The following examples will further illustrate the invention. In the statements regarding the compositions used in these examples the fact that the balance is iron is not specifically mentioned.

EXAMPLE 1 This Example illustrates the properties of different shaped bodies having slightly different compositions when made by the process of the invention.

This Example illustrates the properties of shaped bodies made from pure sintered iron, from a sintered iron alloy containing copper and a sintered iron alloy containing copper and nickel. In all cases the sintering of the shaped bodies was effected for 60 minutes at 1 C in a protective gas atmosphere.

The results appear from the following TABLE I] I ll Ill Sintered lron Sintered iron with 2 wt. 7r Sintered lron With 2 Wt.%Cu each. Cu and Ni v y: lglcm l 5:% v zlkp/mm l 81%] ozlkplmm 6: '70] o' :[kp/mm I 6.3 lO-ll 12 3-4 21 3-4 23 II 7.0 l7-l8 7-8 29 7-8 32 This Example permits to compare the sintered bodies and Sintering process of the invention with prior art alloys and processes. As appears the formed bodies of the invention and the sintering process permit to obtain values of elongation at break and tensile strength which are more or less equivalent to the values obtainable with the iron-copper-nickel sintered alloys. However,

this can be accomplished with a considerably smaller 20 processing effort and expense.

EXAMPLE 3 This Example illustrates the first of the three alternative sintering processes identified above as A. The results appear from the following Table.

EXAMPLE 4 This Example illustrates the process identified above as B. The results appear from the following Table IV.

h u TABLE III Composition and Sintering Elonga- Density (y) of Temp. and Quenching tion at Tensile the Shaped Body Time Cooling Temp. Break Strength 51%] 07;:[kp/mm I I9? tin. 4% copper 950C, 2025C 580C 9.5 29.5

20 min. per min. Sn:Cu 1:4 7.0 g/cm same same 750C 30.8

TABLE IV Composition and Sintering Tempering Elonga- Tensile Density (7) of Temp. and Temp. tion at Strength the Shaped Body Time Cooling and Time Break cr Z[kp/mm l 1% tin, 4% copper 950C, slowly 20 min. to room temp. Sn: Cu 1:4 550C 2h 6.5 30 'y 7.0 g/cm 650C 2h l2 26.5

ll 1% tin, 2% Copper do. do. 650C 2h 9.5 26.5

Sn:Cu 1:2 7 7.0 g/cm Ill 1% tin, 6% copper do. do. 650C 2h l2 26.5

Sn:Cu l :6 y 7.0 g/cm The optimum tempering temperature can again be determined by consulting the attached drawing which shows which tempering temperature should be used to obtain a specific elongation or specific tensile strength.

l. The process of making a sintered shaped body comprising forming a pulverulent mixture of 0.5 to 3% tin, 2 to 14% copper, balance iron, the ratio of tin to copper being between 1:2 and 1:9; subjecting the said 5 mixture to sintering in the desired shape; and immedi- EXAMPLE 5 ately after said sinteringQCoolingthe shaped body at a This Example illustrates the process above identified speed of 15C/min to a temperature between about as C. The results appear from the following Table. 520 and 750C followed by chilling.

10 TABLE V 7 Sintering Elongation Tensile Composition and Temp. and at Break Strength Density (y) Time Cooling 8:[%] o' :[kp/mm 1% tin, 4 7r copper 950C, 27Clmin 12.5 27

min. to 300C Sn:Cu l:4 7.0 g/cm Most of the data furnished in the above examples 2. The process of making a sintered shaped body have been provided for a density of the shaped body of comprising forming a pulverulent mixture of 0.5 to 3% 7.0 g/cm in order to enable a reasonable comparison tin, 2 to 14% copper, balance iron, the ratio of tin to between the different values. At lower d ensities lower copper being between 1:2 and 1:9; subjecting the said values are obtained. mixture to sintering in the desired shape; and immedi- It will also be noted that with a tempering temperaately after said sintering slowly cooling the shaped body ture outside the range of the present invention someto room temperature, whereupon it is tempered for bewhat lower values were obtained for the elongation at tween 15 minutes and 5 hours at a temperature bebreak (see Table IV, compound I, first process). tween 520 and 750C followed by quenching.

Without further analysis, the foregoing will so fully 3. The process of making a sintered shaped body reveal the gist of the present invention that others can comprising forming a pulverulent mixture of 0.5 to 3% by applying current knowledge readily adapt it for varitin, 2 to 14% copper, balance iron, the ratio of tin to ous applications without omitting features that, from copper being between 1:2 and 1:9; subjecting the said the standpoint of prior art, fairly constitute essential mixture to sintering in the desired shape; and immedicharacteristics of the generic or specific aspects of this ately after sinering cooling the shaped body at a rate of invention and, therefore, such adaptations should and E 27 C/min to a temperature of 300C whereupon it are intended to be comprehended within the meaning is permitted to cool down in a protective gas atmoand range of equivalence of the following claims. sphere.

What is claimed as new and desired to be protected 0 by Letters Patent is set forth in the appended claims: 

1. THE PROCESS OF MAKING A SINTERED SHAPED BODY COMPRISING FORMING A PULVERULENT MIXTURE OF 0.5 TO 3% TIN, 2 TO 14% COPPER, BALANCE IRON, THE RATIO OF TIN TO COPPER BEING BETWEEN 1:2 AND 1:9; SUBJECTING THE SAID MIXTURE TO SINTERING IN THE DESIRED SHAPE; AND IMMEDIATELY AFTER SAID SINTERING, COOLING THE SHAPED BODY AT A SPEED OF 15*C/MIN TO A TEMPERATURE BETWEEN ABOUT 520 AND 750*C FOLLOWED BY CHILLING.
 2. The process of making a sintered shaped body comprising forming a pulverulent mixture of 0.5 to 3% tin, 2 to 14% copper, balance iron, the ratio of tin to copper being between 1:2 and 1: 9; subjecting the said mixture to sintering in the desired shape; and immediately after said sintering slowly cooling the shaped body to room temperature, whereupon it is tempered for between 15 minutes and 5 hours at a temperature between 520* and 750*C followed by quenching.
 3. The process of making a sintered shaped body comprising forming a pulverulent mixture of 0.5 to 3% tin, 2 to 14% copper, balance iron, the ratio of tin to copper being between 1:2 and 1: 9; subjecting the said mixture to sintering in the desired shape; and immediately after sinering cooling the shaped body at a rate of > or = 27 C/min to a temperature of 300*C whereupon it is permitted to cool down in a protective gas atmosphere. 